Update to the monetization API

[vicky5124]

The Discord API documentation updated with a few changes:

• Added a new sku_id field to the interaction buttons model.
• Added a new button style.
• Updated the conflicts between button fields.
• Deprecated the PREMIUM_REQUIRED interaction response type.
• Added 2 new links to store items (Entitlement and Sku could implement methods that could return these URLs):
  • https://discord.com/application-directory/:appID/store
  • https://discord.com/application-directory/:appID/store/:skuID